#include <bits/stdc++.h>
using namespace std;
int main()
{int n,g,s,b,q;
cin>>n;
g=n%10;
s=n/10%10;
b=n/100%10;
q=n/1000;
cout<<g+s+b+q; 
	return 0;
	}
/**************************************************************
	Problem: 1390
	User: lyy002
	Language: C++
	Result: Accepted
	Time:15 ms
	Memory:2072 kb
****************************************************************/